Police arrested nearly two dozen people in Ferguson during a protest marking the anniversary of the fatal shooting of an unarmed 18-year-old African-American by a white police officer, although there was no repeat of the violence that scarred weekend demonstrations.

Police arrested nearly two dozen people in Ferguson during a protest marking the anniversary of the fatal shooting of an unarmed 18-year-old African-American by a white police officer, although there was no repeat of the violence that scarred weekend demonstrations.

There were no shots fired and no burglaries, looting or property damage during the protest, police said.

The St Louis suburb thoroughfare was the focus of months of massive protests and sometimes violent unrest last summer after the killing of Michael Brown by a Ferguson police officer, which sparked nationwide protests and a fierce debate over how police treat minorities.

On Monday night, no smoke or tear gas was used and no police or civilians reported injuries. By 1am, the crowd and police were heading home. Police said approximately 23 arrests were made, although they were still confirming official totals.

Late on Sunday, a protest in the same area was interrupted by gunfire and a police shooting that left an 18-year-old suspect critically injured. The violence set Ferguson on edge and had protest leaders worried that tensions could escalate.

St Louis County Executive Steve Stenger declared a state of emergency that authorised county police chief Jon Belmar to take control of police emergency management in and around Ferguson.

Early on Monday evening, hundreds of protesters were chanting, beating drums and carrying signs.

When some in the group moved into a traffic lane, police officers in riot gear forced people out of the street. Some demonstrators threw water bottles and other debris at officers.

Protests also cropped up outside Ferguson. Almost 60 people, including scholar and civil rights activist Cornel West, were arrested for blocking the entrance to the federal courthouse in downtown St Louis.

Another group later briefly blocked a highway during the afternoon rush hour.

At the Sunday night demonstration, tensions escalated after several hundred people gathered in the street, ignoring repeated warnings to get to the sidewalk or face arrest.

Several gunshots rang out from an area near a strip of stores, including some that had been looted moments earlier. The shots sent protesters and reporters running for cover.

Police Chief Jon Belmar said he believed there were six shooters, including 18-year-old Tyrone Harris Jr (18), who the police chief said had opened fire on officers.

Mr Harris Jr was arrested during the violence and was in a critical condition in hospital after surgery.

Prosecutors announced 10 charges against him - five counts of armed criminal action, four counts of first-degree assault on a law-enforcement officer and a firearms charge.

Mr Harris's father called the police version of events "a bunch of lies".

Tyrone Harris Sr said two girls who were with his son told him the 18-year-old was unarmed.

They said he had been drawn into a dispute involving two groups of young people and was "running for his life" after the gunfire broke out.

He said his son was a close friend of Michael Brown and had been in Ferguson on Sunday night to pay respects.

"My son was running to the police to ask for help and he was shot," Mr Harris Sr said. "It's all a bunch of lies ... They're making my son look like a criminal."

Online court records show that Tyrone Harris Jr was charged in November with stealing a motor vehicle and a gun, as well as resisting arrest by fleeing.

Mr Belmar said the suspect who fired on officers used a stolen semi-automatic 9mm gun.